Sound recording



Dec. 2, 1941. .Q D|MM|K 2,265,103

- soUND RECORDING Filed June 29, 1939 fsnucntor Patented Dec. 2, 1941SOUND RECORDING Glenn L. Dimmick, Haddonield, N. J., assignor to RadioCorporation of America, a corporation of Delaware .I ApplicationJune-29, 1939, serial No. .281,819

6 claims. (o1. 179-1093) This invention relates to sound recording andmore particularly to the photographic recording of sound on nlm. Inrecording sound on film it occasionally is desirable toproduce anextremely wide sound record in which case a recording light of unusuallyhigh intensity must be used. Likewise, in recording sound on very slowfine grained film it is sometimes desirable to use a recording light ofhigh intensity. One type of lamp which is available for the purposeandwhich is quite satisfactory is what is known commercially as a highpressure mercury vapor lamp.

In the older mercury vapor lamps, themercury vapor was operated at arelatively low pressure and the light produced had a comparatively lowintrinsic brilliancy. In a type of mercury lamp now available, themercury vapor is operated at a relatively high pressure and the lightproduced has a correspondingly high intrinsic brilliancy. In theoperation of such lamps there are diiiiculties encountered due to theirpeculiar thermal characteristics. Whe-n the lamp islrst turned on ittakes a considerable .time until it reaches equilibrium and the lightremains of constant brilliancy. If the current throughthe lamp ischanged it again takes several minutes for the lamp to reach a steadyconditi-on and the brightness of the light which will result can not bedirectly determined at the time the current is changed. For thesereasons, it is unsatisfactory to control the brightness of the recordinglamp in the manner customary for incandescent lamps where the brightnessis controlled by a series resistance.

In the use of these mercury vapor lamps, I find it quite satisfactory tobring the lamp to equilibrium at a brightness slightly greater than thatnecessary in the recording and to then optically control the amount oflight transmitted through the optical system so as to provide the properlight intensity at the lm. This light control may be accomplished in anydesired manner but I prefer to accomplish the result by a pair ofshutters located immediately in front of the galvanometer mirror in therecording system.

One object of the invention is to provide an improved sound recordingoptical system.

Another object of the invention is to provide an improved apparatus forcontrolling the intensity of the sound recording light.

Another object of the invention is to provide an improved type ofdiaphragm for controlling the light intensity in sound recordingsystems.

Other and incidental objects of the invention will be apparent to thoseskilled in the art from a reading of the following specification andinspection of the accompanying drawing in which Figure l is a top viewpartly in section of a recording optical system illustrating theinvention, and

Figure 2 is a section taken on the line 2-2 of Fig. 1 and looking in thedirection indicated by the arrows.

Referring first to Fig. 1, the high pressure mercury vapor lampI isindicated generally at I0. Light from this lamp passes through theoptical barrel II to the galvanometer I2 where it is reflected by themirror I9- and passes throughv the second optical barrel I3 to the iilmF.

'Ihe iirst optical barrel is provided with a condenser lens I4 whichconverges the light through an appropriately shaped aperture I5 adjacentwhich are located the ground noise reduction shutters I6 and I1 and thelight then passes through the lenses I8 which direct it upon thegalvanometer mirror I9. The mirror I9 is vibrated about an axis in theplane of the paper 't in accordance with the sound waves to be recordedand directs the vibrated beam through the lens 20 to the slit plate 2|which is provided with a narrow slit in the plane of the paper. Lightpassing through the slit 2I is focused by the objective lens 22 upon theiilm F in the form of a narrow line. This objective lens may be made asdescribed and claimed in my concurrently led application entitled Soundrecording optical system, identied as RCV Docket No. 6889, whichdiscloses in detail an objective lens particularly adapted for themaking of wide sound records.

The galvanometer I2 is provided with a pair of shutters 29 and 30arranged in front of the mirror I9 and within the galvanometer casing.In order to decrease the light intensity these shutters are moved towardeach other across the galvanometer mirror and thus serve as a diaphragm.In the optical system just described the light source I 0 is imaged uponthe galvanometer mirror I9, the aperture I5 is imaged by the lenses I 8and 29 upon the slit plate 2| and the galvanometer mirror I9 is imagedby the lens 20 at the entrance pupil of the objective 22 which has theslit plate 2I and the film F at its conjugate foci. Due to thisarrangement the shutters 29 and 30 are located at an aperture stop ofthe optical system in relation to the image formed upon the iilm F andtherefore movement of these shutters produces a change in in.

tensity Without any change in position or dimensions of the image uponthe film.

The shutters 29 and 30 are controlled as follows: The galvanometer iscarried in a pair of supports 23 and 24. One of these supports carriesan appropriate screw 25 which serves as a pivot for the galvanometer andwhich is locked in position by an appropriate lock nut 26,. Coaxial withthe screw 25 there is provided a second screw 21 which also serves as apivot for the galvanorneter. This screw 21, however, moves. freely inthe support 24 and is threaded into the casing of the galvanometer l2.It will be appar-A ent that due to the sliding relation of the screw 21to the support 24 it may be-moved in and out Without affecting thesupport of the galvanometer. The end of this screw 21 bears against aspring 33 which is attached tothe shutters 2,9. and 30. These shuttersare pivoted to, the gala, vanometer casing at 3l and 32. When the screw111 is turned by the knugledhead 28 it; moves they middle ef the Spring3.3? incr entend causes Corresponding; movement ef the Shutters 29 and39 about their rivets therebyI Causing the shuttees; te Obscure merelerl lese of the area oi the mirror; I9 or,n as shown inv Eig. 2, more orless of the galvanometer window 34.

It, will be apparent that my. invention is not limitedto the usel of a,specific shutter arrangement shown but that I may use other appropriatediaphragm means which may be located either adiaeent the ealvanemetermirror er at. any other point, in the optical systemlwhich serves as anaperture Stop ef the erstem in relatgen to. the image en the lmy F. Forexample, the dia-.- phragm might, be located adziacentY the entrancepupil of the Objective 22 where the; image of; the mir-rer I9 is formeder even. adjacent. the.- lamp I8.- Tlee light control device is.preterably 1oeated at some peint, in the optical system between thelight sourcey and the place Where the, light beam is eXamir-ledy forintensity. The4 measurea ment of the, intensity of the light may: beaccom.- plished by an appropriate exposure meter and' a mcwabler mirrorin the manner described, for example, in Zimmerman application SerialNo. 248,250, flied December 29, 1938*` I he apparatus of the presentapplication is an improvement on that described.l and claimed in theapplication of E. W. Kellogg, Serial No.

280,960, filed June 24, 1939; and is also related to the subject matterof the application of L. T. Sachtleben, Serial No. 281,951, filed June29, 1939,

I claim as my invention:

1. In combination, a light source, lens means focusing light from saidsource upon a galvanometer mirror, further lens means directing lightreflected from said mirror inthe form of a ne lineupon a lilm, and:light.. intensity control means located adjacent said galvanometermirrQr.

2. In combination, a light source, lens means fecnsingv light from saidsource upon a galvanometer mirron further lens means directing lightreectedfrom said mirror in the form of a ne line upon al nlm, and anadjustable diaphragm located adjacent said galvanometer mirror.

3. In combination, a light source, lens means focusing light from saidsource upon a galvanom eter mirror, further lens means directing lightreflected from said mirror inthe form of a ne line upon a record strip.and an adjustable diaphragm` located. adjacent said galvanometermirrorisaid diaptnagm including a: pair of adj'nstable blades; movedacross the said mirror on; opposite sid-es.

4. In combination, a. highv pressure mercury vapor lamp., lensv meansfocusing light from said lamp.V upon a galvanometer mirror, further lensmeansv directing light. reflected from said mirror in the form of a fineline upon a ihm, and; light intensity control means located adjacentsaid galvanometer mirror.

5. In combination, a high pressure mercury vapor lamp, lens meansfocusing light from said lamp. upon a galvanometer mirror', further lensmeans: directing, light reflected from said mirror in the formof a: finelineupon a film, and an adjustable diaphragm located adjacent saidgalvanometer mirror.

6. In combination, a high pressure mercury vapor lamp, lens meansAfocusing light from. said lamp upon a galvanorneter` mirror, furtherlens meansA directing light reflected' from said mirror intheform: afanne linev upon a record strip, and an adjustable diaphragm locatedadjacent said galvanometermirror, said diaphragm including a pair ofadjustable blades moved across thesaid mirror on opposite sides.

- GLENN LDIMMICK.

